WO2018216931A1

WO2018216931A1 - Ship including vortex generating fins

Info

Publication number: WO2018216931A1
Application number: PCT/KR2018/005370
Authority: WO
Inventors: 이승호
Original assignee: 필드지 주식회사
Priority date: 2017-05-24
Filing date: 2018-05-10
Publication date: 2018-11-29
Also published as: KR20180128804A

Abstract

According to one embodiment of the present invention, a ship comprises: a hull; a propeller provided at the rear of the hull; and vortex generating fins respectively arranged at optimal points (Po) of the port and the starboard of the hull, and generating a vortex so as to change a flow field passing a rotational surface of the propeller. The optimal point (Po) is positioned 0-0.1 stations apart toward a stem along a reference streamline (Sr), in which a limiting streamline flowing along the surface of the hull passes a reference point (Pr), which is closest to the stem, among the intersecting points when viewed from the side of the hull, when the flow field around the hull is simulated on the assumption that the ship operates at a design speed before the vortex generating fins are arranged on the hull. The reference streamline (Sr) is the limiting streamline positioned lower at the stem side, between two limiting streamlines passing the reference point (Pr).

Description

Vessels containing vortex generating pins

The present invention relates to a vessel comprising a vortex generating pin for regulating the flow of fluid flowing around the hull to improve the efficiency of the propeller and reduce the resistance of the hull.

There is a pair of strong bilge vortices that move from the bottom of the side of the center parallel to the stern at low or medium speed hypertrophy. The bilge vortex flows into the propeller upper surface and becomes a hook shape from the point where the vortex is generated to the propeller. This low speed region causes non-uniform velocity distribution on the propeller rotational surface, which causes deterioration of the performance of the propeller.

Recently, as the size of the ship progresses, the size of the low speed region increases, and a problem of hull vibration caused by the cavitation occurs, which is an urgent issue. At this time, the shape of the hull and the propeller is left as it is, and a method of attaching an adduct such as a vortex generator or a vortex generating fin in order to alleviate the nonuniformity of the axial velocity distribution flowing into the rotating surface of the propeller. Is being proposed.

When the low speed vessel travels at a constant speed, the fluid around the hull parallel flows parallel along the side of the hull. However, at the rear of the hull parallel part, the streamline flowing in parallel to the side of the hull crosses the streamlined protrusion protruding toward the stern at the lower side of the inclined surface for the installation of the propeller. Downflow to) occurs.

On the other hand, since the streamline at the bottom of the hull causes a bilge vortex and faces the hub of the propeller, upward flow occurs at the stern near the propeller. At this time, the downward flow and the upward flow cross each other up and down when looking at the hull from the side. On the other hand, such downflow and upflow form a rotating flow flowing around the hub to which the propeller is attached to weaken the propulsion performance of the propeller.

That is, in the low speed vessel in which the shape of the stern portion is rapidly changed, the limit stream line may deviate from the shape of the hull at the stern portion, and the resistance increases along with the flow separation phenomenon.

The present invention is to solve the various problems including the above problems, the resistance and cavitation of the hull through the vortex generating pin to generate a vortex to change the flow field passing through the rotating surface of the propeller It is an object of the present invention to provide a vessel that can reduce vibrations and increase thrust efficiency of propellers.

Ship according to an embodiment of the present invention, the hull; A propeller installed at the rear of the hull; And a vortex generating fin disposed at an optimum point Po of the port and starboard of the hull, respectively, to generate a vortex to change the flow field passing through the rotating surface of the propeller.

The optimal point Po is a limiting stream flowing along the surface of the hull when simulating the flow field around the hull assuming that the vessel is maneuvering at a design speed before the vortex generating pin is placed on the hull. A limiting streamline is located 0 to 0.1 stations away in the bow direction along the reference stream line Sr passing through the reference point Pr closest to the bow side of the intersection points when viewed from the side of the hull.

The reference streamline is a limit streamline located further down the bow side of the two limit streamlines passing the reference point.

In one embodiment, the vortex generation pin may be arranged such that the angle of attack with the reference stream line is 2 ~ 20 °.

In one embodiment, the length of the vortex generating pin may be 1% to 3.5% of the repair length of the hull.

In one embodiment, the height of the vortex generating pin is 0.1 to 0.2% of the repair length of the hull, the thickness may be about 5mm to 15mm.

In one embodiment, the design speed of the vessel may be about 15 knots or less, and the block coefficient of the hull may be 0.8 to 0.85. That is, the vessel according to the present invention may be a vessel classified as a low speed vessel.

According to the ship according to an embodiment of the present invention, the optimum point Po is the vortex generating pin is arranged to straighten the rotational flow near the propeller, to simplify the complex flow to increase the thrust efficiency, to thin the thickness of the boundary layer As a result, the resistance is reduced, and the flow velocity of the upper end of the propeller is increased, thereby reducing the stern vibration caused by the cavitation. On the other hand, the ship's design can be easily derived from the reference point and the reference streamline, which can be known from the simulation results without the vortex generating pin, without having to go through a number of time-consuming and costly simulations. Save money and time.

FIG. 1 is a perspective view showing a limiting streamline flowing along the starboard of a stern before the vortex generating pin is disposed, which is obtained through computer simulation using computational fluid dynamics (CFD).

FIG. 2 is a right side view schematically showing the limit stream line flowing along the starboard of the stern before the vortex generating pins are disposed; FIG.

3 is a right side view schematically showing the limit stream line flowing along the starboard of the stern after the vortex generating pins are disposed.

4 is a perspective view showing a limit stream line flowing along the starboard of the stern after the vortex generating pins are disposed through computer simulation using computational fluid dynamics (CFD).

5 is a diagram showing the velocity distribution of the fluid around the ship and the hull in which the vortex generating pins 30 are arranged.

6 is an experimental graph showing a change in resistance according to the presence or absence of vortex generating pins.

FIG. 7 is a diagram comparing isoflow velocity diagrams of stream lines with or without vortex generating pins in a cross section taken along line P1 of FIG. 4A.

FIG. 8 is a right side view schematically illustrating a vessel in which vortex generating pins having different angles of attack (AOA) with reference stream lines are arranged.

FIG. 9 is an experimental graph showing a time-dependent resistance acting on a vessel having a vortex generating pin having different angles of attack.

10 is a diagram comparing the isoflow velocity diagram at the cross section through a propeller of a vessel having a vortex generating pin with different angles of attack.

11 is a perspective view of the hull stern showing the vortex generating pins of various lengths.

12 is a perspective view showing a simulation of a limit stream line flowing around a ship having vortex generating pins having different lengths.

FIG. 13 is an experimental graph showing a time-dependent resistance acting on a vessel having vortex generating pins having different lengths.

14 is a diagram comparing the isoflow velocity diagram according to the length of the vortex generating pins.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail. Effects and features of the present invention, and methods of achieving them will be apparent with reference to the embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various forms.

In the following embodiments, the terms first, second, etc. are used for the purpose of distinguishing one component from other components rather than having a limiting meaning.

In the following examples, the singular forms "a", "an" and "the" include plural forms unless the context clearly indicates otherwise.

In the following examples, the terms including or having have meant that there is a feature or component described in the specification and does not preclude the possibility of adding one or more other features or components.

In the drawings, components may be exaggerated or reduced in size for convenience of description. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, and thus the present invention is not necessarily limited to the illustrated.

In the present specification, the x axis is the axis passing through the ship's bow and stern, the y axis is the axis passing through the ship's port and starboard, and the z axis is the axis passing through the ship's bottom and upper deck.

In the present specification, the design speed is a speed that can be achieved at 85% or 90% of the maximum power of the main engine mounted on the ship, and means the speed that the shipyard must satisfy as a contract condition in the ship construction contract. .

In the present specification, a station (ST) refers to a boundary between respective sections after dividing the length between perpendicular (L.B.P.) into 20 equal sections. The stations are numbered sequentially from the stern, with the first station numbering 0 and the last station numbering 20. Length between repairs (L.B.P.) means the distance between the fore perpendicular (F.P.) and the after perpendicular (A.P.). F.P. means a line drawn vertically after the intersection of the designed load water line (D.L.W.L.) and the front of the forebody. A stern line (AP) means a line drawn vertically from the back of the other state on ships with a clear rudder post; otherwise, a vertical line passing through the intersection of the center line of the rudder stock and the planned full line draft to be.

In the present specification, the length water line (L.W.L.) of the hull means the distance from where the front surface of the planned full draft line meets the water surface to where the water surface on the stern side meets.

In the present specification, the starboard is described as a center, but the principles and effects described below may be applied symmetrically to the port.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be denoted by the same reference numerals, and redundant description thereof will be omitted. .

Figure 1 shows a limiting streamline (S) flowing along the starboard at the stern before the vortex generating pins (FIGS. 3 and 30), which are derived from computer simulation using computational fluid dynamics (CFD), It is a perspective view shown. 1 shows only the starboard of the stern part of the hull.

Referring to FIG. 1, the limit stream flowing along the surface of the hull 10 in the flow field around the hull 10 assuming that the vessel before the vortex generating pin 30 is placed starts at the design speed. Line S is shown. In the following, the limit stream line will be abbreviated as stream line. Such a shape of the stream line (S) can be found through a simulation, where 'simulation' may include a computer simulation using computational fluid dynamics (CFD) or a model simulation using a model ship. In this case, the shape of the limit stream line S derived through the simulation may be different according to the shape of the ship and the design speed (or the speed of the fluid passing around the ship). However, if the shape and design speed are fixed, the shape of the limit streamline S around the hull 10 can be clearly defined through simulation.

In the experimental example of FIG. 1, the streamline flowing parallel to the side of the hull 10 near the two stations 2ST and 50% in height between the bottom and the design draft Td is the hub of the propeller hub, 20H. Towards) downward flow occurred. In addition, the stream line flowing from the bottom causes bilge vortex (V _b ), and upward flow occurred toward the hub 20H. As described above, such downflows and upward flows form a rotating flow that rotates near the hub 20H to which the propeller is attached, thereby weakening propulsion performance of the propeller.

One embodiment of the present invention solves the above-described problem by placing the vortex generating pins 30 on the port and starboard of the hull 10, respectively. That is, the ship according to an embodiment of the present invention, the hull 10; A propeller 20 installed at the rear of the hull; And a vortex generating pin 30 disposed at an optimum point Po of the stern portion of the port and starboard of the hull 10 to generate a vortex to change the flow field of the rotating surface of the propeller 20.

At this time, the present invention uses the concept of 'reference point (Pr)' and 'reference streamline (Sr)' to derive the optimum point (Po) in which the vortex generating pins 30 are disposed. This is described below.

FIG. 2 is a right side view schematically showing the limit stream line S flowing along the starboard of the stern before the vortex generating pin 30 is disposed. In FIG. 2, only the lower portion of the stern draft Td is illustrated.

Streamline refers to the path of fluid particles over time. According to this definition, streamlines do not intersect with each other when viewed in three dimensions. However, when looking at the hull in a specific direction as shown in Figure 2, the streamlines appear to cross each other.

In the present specification, 'intersecting' the streamline means that the 'projection' of the xz-plane of the streamline intersects when the hull is viewed in a direction parallel to the y axis. In this case, in computer simulation, the angle of view of the modeled hull is adjusted, and in the case of model simulation, the photograph is taken with a line of sight parallel to the y axis. I can understand it. In FIG. 2, some of the intersection points of the stream lines are indicated by x characters.

At this time, the point closest to the player side among the several points where the limit stream line S intersects is defined as the reference point Pr. That is, on the xz-plane, the reference point means the point where the x coordinate is largest among several points where the limit streamline intersects. In this case, the reference point Pr may mean a point where the downflow and the upstream begin to cross each other. The position of the reference point Pr may be clearly defined within an error range of the size of the lattice in the case of computer simulation and the spacing of the paint lines representing each streamline in the model simulation.

That is, the position of the reference point Pr can be derived by simulating the flow field around the hull, assuming that the ship starts at a design speed before the vortex generating pins 30 are arranged on the hull 10.

Hereinafter, the reference stream line Sr passing through the reference point Pr is defined. Since the point at which the streamlines (orthogonal projections of) are 'intersected' with each other on the xz-plane is defined as a reference point, the two streamlines (orthogonal projections of) pass through the reference point Pr. In FIG. 2, these two streamlines are represented as Sr and Sx. In this case, the reference stream line Sr means a stream line located further below (the bottom side) from the athlete side of the two stream lines. That is, the reference stream line Sr may be one of streamlines included in the upstream, and may be one of streamlines separated from the hull surface by generating a bilge vortex (Vb) from the bottom of the hull. On the other hand, another stream line (Sx) passing through the reference point may be one of the stream lines included in the down stream.

The optimum point Po on which the vortex generation pin 30 is disposed is derived using the reference point Pr and the reference stream line Sr described above.

According to the present invention, the optimum point Po of the stern portion in which the vortex generating pins 30 are disposed is located at 0 to 0.1 station in the bow direction along the reference stream line Sr. The 0 to 0.1 stations are based on the x coordinate of the ship, not based on the curve length of the reference streamline. Referring to FIG. 2, a line SSa passing through the reference point Pr and parallel to the z-axis and a parallel line SSb separated by 0.1ST from the line SSa is shown. In FIG. 2, the length of 0.1ST is exaggerated for convenience of description.

At this time, when the point where each line (SSa, SSb) and the reference stream line (Sr) meets A, B, the optimum point (Po) where the vortex generating pin 30 is to be arranged is any point of the curve AB, that is, It is placed on the thicker curve in 2. At this time, the vortex generation pin 30 may be disposed such that the point closest to the bow is positioned at the optimum point Po.

The inventors found out that through the simulation of various low speed vessels, the optimum point Po can be derived from the above-mentioned reference point Pr and the reference stream line Sr, which is applied to various vessels, not specific vessels. It was.

3 is a right side view schematically showing the limit stream line S flowing along the starboard of the stern after the vortex generating pin 30 is disposed. 3 also shows only the lower portion of the stern draft Td.

Referring to FIG. 3, the flow field behind the vortex generating pin 30 (stern side) is changed by the vortex generating pin 30 to change the thickness of the boundary layer and the flow field passing through the rotating surface of the propeller 20. On the other hand, the flow field in front of the vortex generating pin (the bow side) does not change. Therefore, even after the vortex generating pin 30 is attached, the reference stream line is maintained as it is only in front of the vortex generating pin (hereinafter, the reference stream line in front of the vortex generating pin will be referred to as Sr '). Therefore, the angle of attack (AOA) between the chord line of the vortex generating pin and the reference stream line Sr 'can be defined irrespective of the change in the flow field with or without the vortex generating pin 30. This will be described later.

4 is a perspective view showing the limit stream line S flowing along the starboard of the stern after the vortex generating pin 30 is disposed, which is derived through computer simulation using computational fluid dynamics (CFD). In FIG. 4, only the starboard of the stern part of the hull 10 is illustrated.

1 and 4, the repair length of the hull 10 was about 181 m, and the position of the vortex generating pin 30 was about 30 cm in the bow direction from the reference point, that is, about 0.03 stations apart. On the other hand, the vortex generating pin 30 has a higher stern side and a lower bow side so that the angle with the reference stream line Sr, that is, the angle of attack is about 6 °. At this time, the angle between the vortex generating pin 30 and the bottom was about 21.42 °.

Comparing FIG. 4 with FIG. 1, after the vortex generating pin 30 is disposed, the rotational flow around the hub 20H on which the propeller (not shown in FIG. 4) is installed changes close to the straight stream. That is, the vortex generating pin 30 may serve to simplify the shape of the complex flow field around the stern. As a result, the flow field passing through the rotating surface of the propeller becomes uniform, and the propulsion performance of the propeller is improved.

When the vortex generating pins 30 are arranged in this way, the thickness of the boundary layer at the stern portion becomes thin, thereby reducing the resistance acting on the hull as a whole.

5 is a diagram showing the velocity distribution of the fluid around the ship and the hull 10, the vortex generating pin 30 is disposed. (A) is a right side view which looked at the stern part from the right side, and (b)-(d) is the iso velocity diagram of a stream line in the cross section cut along the P2, P3, P4 line | wire in (a), respectively. Indicates a distribution. At this time, the left side of each isoflow velocity diagram shows a state in which the vortex generating pin 30 is attached, and the right side shows a state in which the vortex generating pin is not attached.

5 (b) to (d) show the speed distribution near the hull surface, and the speed of the ship is indicated by a line divided by ten. The design speed of the simulated vessel was 14 knots, and the speed of the fluid to match the Froude number in the computer simulation was 1.273 m / s. At this time, when comparing the left and right sides of the (b) to (d) iso velocity diagram, a difference in velocity distribution occurred depending on whether the vortex generating pin 30 was attached. That is, in the left figure where the vortex generating pin 30 is attached, it can be seen that the velocity of the fluid flowing around the lower surface of the hull is increased as compared with the right figure. That is, a difference occurs in the thickness of the boundary layer depending on whether or not the vortex generating pin 30 is attached, and the difference occurs in the resistance acting on the hull.

The vortex generating pin 30 itself acts as a resistance because it hinders the flow of fluid flowing around the hull 10, but the flow field behind the vortex generating pin 30 in the direction of increasing the velocity of the fluid around the hull 10. By changing the size of the resistance acting on the entire ship can be reduced.

6 is an experimental graph showing a change in resistance according to the presence or absence of vortex generating pins. Referring to FIG. 6, a change in resistance magnitude with time is shown. In the above experimental example, the vortex generating pin was arranged such that the angle of attack was 6 ° at a distance of 30 cm along the reference stream line, that is, about 0.03 stations. In this case, when the vortex generating pin is attached, the resistance is reduced by about 5% on average than when the vortex generating pin is not attached.

That is, according to an embodiment of the present invention, the resistance may be reduced by about 5% by merely placing the vortex generating pins 30 at the optimum points Po of the left and right strings of the hull. At this time, since the optimum point Po can be immediately known from the simulation result of the hull 10 in which the vortex generating pin 30 is not disposed, the vortex generating pin can reduce the resistance of the ship without performing the simulation several times. 30) can be found.

On the other hand, when the vortex generating pin 30 is disposed at the optimum point Po described above, the resistance is reduced and the vibration caused by the cavitation is also reduced, which will be described below.

It is known that the vibration caused by the cavitation can be reduced when the flow velocity in the region between 10 o'clock and 2 o'clock is accelerated around the hub 20H of the propeller. That is, by increasing the flow rate of the stream line flowing in the upper portion of the propeller, it is possible to reduce the vibration. In this case, the velocity distribution in the area shown in the lower part of FIG. 7 shows that the velocity of the stream line flowing in the upper portion of the propeller is relatively higher than when the vortex generating pin is attached (left) and the vortex generating pin is not attached (right). You can see it's fast.

According to an embodiment of the present invention, the vortex generating pin 30 is disposed at the optimum point Po derived from the reference point Pr, which can be known from one simulation, and is generated by the hull resistance and the cavitation. The effect of reducing vibration can be obtained.

FIG. 8 is a right side view schematically showing a vessel in which the vortex generating pins 30 having different angles of attack (AOA) with reference stream lines are arranged.

According to one embodiment, the vortex generating pin 30 may be arranged such that the angle of attack with the reference stream line Sr 'is 2 to 20 °.

As described above, the reference stream line Sr is defined in the flow field in the absence of the vortex generating pin 30, but is located in front of the vortex generating pin 30 (the bow side) even when the vortex generating pin 30 is disposed. There is no change in the streamline. Therefore, the angle of attack (AOA) between the portion Sr 'positioned on the bow side of the reference stream line Sr and the vortex generating pin 30 is constant regardless of the presence or absence of the vortex generating pin 30. Can be defined. In the above experimental example, the vortex generating pin 30 is disposed to have an angle of 6 ° with the reference stream line Sr ', that is, the angle of attack is about 6 °.

In this case, when the angle of the vortex generating pin 30 is adjusted, a change occurs in the stream line flowing through the vortex generating pin 30, thereby changing the resistance characteristic and the cavitation characteristic of the hull. 8, the vortex generating pins 31, 32, 33, 34, and 35 whose angles of attack are changed by -4, 0, +4, +8, and + 14 ° from the reference vortex generating pins having the angle of attack of 6 ° are respectively shown. Is shown. That is, in one experimental example, the change in the flow field by the vortex generating pins 31, 32, 33, 34, and 35 with the angle of attack of the reference stream line Sr 'at 2, 6, 10, 14, and 20 °, respectively, Simulated. Hereinafter, each of the vortex generating pins 31, 32, 33, 34, and 35 will be represented by pins 1 to 5.

FIG. 9 is an experimental graph showing a time-dependent resistance acting on a vessel having a vortex generating pin having different angles of attack. Referring to FIG. 9, the vortex generating pins 31, 32, 33, 34, and 35 having angles of attack of the pins 1 to 5, that is, the reference streamline Sr 'are 2, 6, 10, 14, and 20 °, respectively. The variation of the hull resistance due to the difference was within about 1%. That is, when the angle of the vortex generating pin 30 is adjusted so that the angle of attack is about 2 to 20 °, the resistance reduction rate may be 4% or more as compared with when the vortex generating pin 30 is not present.

On the other hand, although not shown, if the angle of attack of the vortex generating pin 30 is greater than 20 °, the effect by the self-resistance of the vortex generating pin 30 becomes noticeable, thereby increasing the resistance. On the other hand, when the angle of attack is smaller than 2 °, the effect of forming the vortex (vortex) by the vortex generating pin 30 is insignificant, so that there is no great difference from the case where the vortex generating pin 30 is not present.

10 is a diagram comparing the isoflow velocity diagram at the cross section through a propeller of a vessel having a vortex generating pin with different angles of attack. In this case, the center region of each box represents the hub portion of the propeller. The difference in velocity distribution near the hub is distinguishable. In the absence of a pin, the relatively low speed range is wider near the bulb.

At this time, when comparing the area between 12 o'clock and 2 o'clock around the hub, it can be seen that the velocity distribution at the top of the propeller gradually increases as the angle of attack of the vortex generating pin 30 increases in a specific range. As described above, when the flow rate of the stream line passing through the upper end of the propeller rotating surface is increased, cavitation is prevented and vibration is reduced. In other words, as the angle of attack increases, vibration decreases.

On the other hand, it is known that the flow velocity passing through the rotating surface of the propeller is preferably distributed evenly over the entire rotating surface in terms of the efficiency of the propeller. That is, the cavitation prevention and propeller efficiency are in a trade-off relationship with each other. In the case of pin 3 (33), the flow velocity distribution on the propeller rotation surface is increased compared to pin 4 (34) or pin 5 (35) while increasing the flow rate above the propeller compared to pin 1 (31) or pin 2 (32). It is constant.

That is, considering both the cavitation and the efficiency of the propeller, the vortex generating pin 30 may be arranged such that the angle of attack is around 10 °, that is, about 6 ° to 14 °.

11 is a perspective view of the hull stern showing the vortex generating pins of various lengths. In FIG. 11, only the starboard of the stern part of the hull 10 is illustrated.

According to one embodiment, the length L of the vortex generating pin 30 may be 1 to 3.5% of the hull repair length.

According to one embodiment, the height of the vortex generating pin 30 may be 0.1 to 0.2% of the hull repair length. In this case, the 'height' may be based on a direction perpendicular to the surface of the hull.

According to one embodiment, the thickness T of the vortex generating pin 30 may be about 5mm to 15mm.

Referring to FIG. 11, the vortex generating pin 30 illustrated in black represents a vortex generating pin (pin 3) having an increased angle of attack of 4 ° from the vortex generating pin (pin 2) of FIG. 4. That is, it is assumed that the vortex generating pin (pin 3) of FIG. 11 forms an angle of 10 ° with the reference stream line Sr.

On the other hand, the length of the vortex generating pin 30 was 2.5 m, about 1.4% of the length of the hull repair, and the height from the surface of the hull was 35 cm, about 0.19% of the length of the hull repair. The thickness of the vortex generating pin 30 was set to about 10 mm.

At this time, in the experimental example of the present invention through the vortex generating pin 30 extending to the point C or D, the change in resistance according to the change in length was measured. The vortex generating pin extending to point C is set to have a length of 50% longer than the reference vortex generating pin shown in black, i.e., about 2.1% of the length of the hull's repair, and creates a vortex extending to point D. The pin was set to be 100% longer than the reference vortex generating pin, ie about 2.8% of the length of the hull's repair.

12 is a perspective view showing a simulation of a limit stream line flowing around a ship having vortex generating pins having different lengths. In FIG. 12, stream streams formed by the vortex generating pins having lengths of (a) without pins and having lengths of (b) 1.4%, (c) 2.1%, and (d) 2.8% of the repair length, respectively.

Referring to FIG. 12A, when there is no vortex generating pin 30, as described above with reference to FIG. 1, the thickness of the boundary layer is large and rotational flow occurs near the propeller, thereby degrading the efficiency of the propeller. On the other hand, in the case of (b), (c), and (d) in which the vortex generating pins 30 are attached to various lengths, as shown in FIG. It is converted and passes over the top of the propeller. At this time, if the length of the vortex generating pin 30 is too short, the rotational flow does not change to a straight stream, and if the length of the vortex generating pin 30 is too long, the straight stream does not pass the propeller rotating surface, which decreases the efficiency of the propeller and the pin itself. Resistance increases.

Referring to FIG. 13, the longer the vortex generating pin 30 is, the larger the resistance increases, but the resistance change is less than 0.2%. On the other hand, although not shown, in the case of the vortex generating pin 30 having a length of 1% and 3.5% of the repair length, the resistance change was about 0.5%. That is, when the length of the vortex generating pin 30 is 1 to 3.5% of the length of the hull, it may bring about a 4.5% or more resistance reduction effect than when the vortex generating pin 30 is not present.

14 is a diagram comparing the isoflow velocity diagram according to the length of the vortex generating pins. The bright area (white area) in the square box shows a relatively low velocity distribution. By attaching a pin, it is confirmed that the flow velocity is increased in this area. The vortex generating pins 30 are arranged such that the angle of attack with the reference stream line Sr 'is 10 °. Referring to FIG. 14, when the length of the vortex generating pin 30 is 1.4%, it can be seen that the velocity distribution at the top of the propeller rotating surface is largest. That is, in terms of cavitation suppression, the length of the vortex generating pin 30 preferably has a length of about 1.4%, that is, about 1 to 2%.

According to the ship according to an embodiment of the present invention, the optimum point (Po) is the vortex generating pin 30 is arranged to straighten the rotational flow near the propeller 20, to simplify the complex flow to increase the thrust efficiency To reduce the thickness of the boundary layer, the resistance is reduced, and the flow velocity of the upper end of the propeller 20 is increased, thereby reducing the stern vibration caused by the cavitation. At this time, the optimal point Po from the reference point Pr and the reference stream line Sr, which can be known from the simulation result without the vortex generating pin 30 without going through a number of simulations, which are time-consuming and expensive. ) Can be easily derived, saving ship design costs and time.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims

hull;

A propeller installed at the rear of the hull; And

In the ship comprising: a vortex generating fin disposed at the optimum point (Po) of the port and starboard of the hull, respectively, to generate a vortex to change the flow field passing through the rotating surface of the propeller;

The optimal point Po,

When simulating the flow field around the hull, assuming that the vessel is maneuvered at a design speed before the vortex generating pin is placed on the hull,

A limiting streamline flowing along the surface of the hull is 0 to the bow direction along the reference stream line Sr passing through the reference point Pr closest to the fore side of the intersection points when viewed from the side of the hull. 0.1 station away,

The reference streamline is a limit streamline located further down the bow side of the two limit streamlines passing the reference point.
The method of claim 1,

The vortex generation pin,

And a receiving angle with the reference stream line is 2 to 20 degrees.
The method of claim 1,

The length of the vortex generating pin is 1% to 3.5% of the length of the repair of the hull
The ship of claim 1, wherein the height of the vortex generating pins is between 0.1 and 0.2% of the length of the hull repair and the thickness is between about 5 mm and 15 mm.
The method of claim 1, wherein the design speed is about 15 knots or less,

The vessel's block coefficient is 0.8 to 0.85.